Centrifugal separators or spin dryers of this general type include a basket rotatably mounted to a support so that the axis of rotation is more or less vertical. The basket usually has a bottom wall, perforate side walls and open top. The material to be dried or otherwise processed is dropped into the basket and the basket is rotated. The resulting centrifugal force thrusts the basket contents radially outward. The solid material is captured by the basket side walls, while any liquid in the basket passes through those walls and is drained away. After a period of time sufficient to substantially dry the solid material in the basket, the basket is stopped and the dried material is removed from the basket.
There exists in the prior art spin dryers that are particularly suited to drying vegetables. A typical such dryer incorporates a rotary basket whose bottom wall is conical and moveable vertically along the axis of rotation of the basket between an upper or closed position wherein the periphery of the conical bottom wall forms a seal with the basket side walls and an open or lower position wherein the bottom wall is spaced well below the basket side walls. At the beginning of the spin cycle, the bottom wall is moved to its closed position and the material to be dried is dropped into the basket from above. The basket is then spun for a selected period of time to dry that material as described above. At the end of the spin cycle, the bottom wall is moved to in its open position allowing the dried material to drop from the basket into a container or onto a conveyor belt. That particular dryer thus simplifies the loading and unloading of the dryer.
However, that prior dryer has several disadvantages which militate against its wider use and application. First, the dryer per se is suspended from an A-frame support structure which limits the direction in which material can be conveyed to and from that dryer. In other words, the dryer basket can only be approached between the A-frames. The support structure also has a relatively large foot print so that the dryer takes up a large amount of floor space in the building in which it is situated.
Another problem with that prior type spin dryer is that the basket bearing housing is mounted to its support by way of a rubber bumper and spherical seat. Accordingly, the dryer tends to vibrate excessively, particularly when carrying an unbalanced load.
Spin dryers with moveable basket bottom walls are disadvantaged also because the bottom wall is invariably mounted at the lower end of a long piston rod that moves the wall between its open and closed positions. Resultantly, when the basket is rotated with that wall in its open position, as occurs at the end of a spin cycle, the shaft experiences shaft run-out which places a considerable amount of stress on the connection between the basket bottom wall and the shaft. Resultantly, fractures may occur at that location necessitating relatively frequent maintenance and repair of the dryer. Often, such repair is difficult because most of the motors and mechanical connections in the prior dryer are located within the A-frame support structure so that they are relatively inaccessible. Consequently, such maintenance and repairs can result in a considerable amount of dryer downtime.
Still further, the pneumatic cylinder portion of the pistion that moves the basket wall usually extends well above the basket, being supported by the A-frame support structure, thereby increasing the overall height of the dryer. For a large capacity dryer which may have a basket diameter as large as four feet, this means that the overall height of the dryer may extend well above eight feet, making it impractical to house the dryer in a building with a standard ceiling height.